The onions will go from white to translucent, and finally will begin to turn golden brown. If the onions are looking dry, add 1-2 additional tbsp. of water, as necessary. Once onions have reached a nice medium golden brown colour, remove from heat and allow to cool slightly. They can be stored for up to 1 week in the fridge.

Prepare the Grilled Cheese

Heat a skillet over medium heat. Spread mayonnaise over both slices of sourdough, then spread Maille® Old Style Mustard over the opposite side of one of the slices.

Place both slices, mayonnaise side down, onto skillet. Dollop the mustard on a slice of bread with caramelized onions and a sprinkle on a few leaves of fresh thyme. Carefully place grated gruyere over the other slice. Cook for 2-3 minutes, until cheese is melted completely. Press sandwich together and serve.